Process for stabilizing polyamides

ABSTRACT

Suitable compounds for stabilizing polyamides against oxidation and thermal degradation are acid amides, acid esters, bis-ureas and bis(acid amides) based on 2,6-di-t-butylphenol-butylamine and 2,6-di-t-butylphenol-butanol of the general formulae:

United States Patent [191 Schlichting et al.

[ PROCESS FOR STABILIZING POLYAMIDES [22] Filed: Feb. 21, 1974 [21] Appl. No.: 444,414

[30] Foreign Application Priority Data Feb. 24, 1973 Germany 2309435 [52] [1.8. CI. 260/453 NC; 260/45.85,R; 260/459 R; 260/4595 H [51] Int. Cl. C08K 5/16 [58] Field of Search r. 260/4595 H, 45.9 NC, 45.9 R

[56] References Cited UNITED STATES PATENTS 4/l973 Heuser et al 260/4595 H l2/l973 Knell 260/459 NC Dec. 9, 1975 Primary ExaminerMelvyn I. Marquis Attorney, Agent, or Firm-Johnston, Keil, Thompson & Shurtleff {57] ABSTRACT Suitable compounds for stabilizing polyamides against oxidation and thermal degradation are acid amides, acid esters, bis-ureas and bis(acid amides) based on 2,6-di-t-butylphenol-butylamine and 2,6-di-tbutylphenol-butanol of the general formulae:

1 HO CH -CH -9-X-H and CH C(CH C 5 H H -l -l- HO CH CH QY CCH OH CH CH 3 5 (Non (M31 6 Claims, No Drawings PROCESS FOR STABILIZING POLYAMIDES This invention relates to a process for stabilizing polyamides against oxidation and thermal degradation.

It is known to stabilize polyamides against the action of heat and air by adding, say, phosphites, complex copper/alkali metal halide compositions, phenolic compounds or aromatic amines.

None of these stabilizers gives perfectly satisfactory results when incorporated in polyamides.

For example, copper salt/halide systems lose their stabilizing activity completely in the presence of certain pigments such as cadmium pigments or SACH- TOLlTl-l (registered trade mark). Other stabilizers, for example the p-phenylene diamine derivatives cause discoloration and are physiologically unsatisfactory. Stabilizers based on kryptophenol are either too volatile for incorporation into the polyamide melt, as in the case of 2,6-di-t-butylphenol for example, or they become discolored, as in the case of 2,2-methylene-bis- (4-methyl-6-t-butylphenol) for example, or they have an inadequate stabilizing action, as for example 1,3,5- trimethyl-2,4 ,6-tri-( 3 ',5 '-di-t-butyl-4 '-hydroxybenzyl benzene and the [3-(3,S-di-t-butyl-4-hydroxyphenyl)- propionate of pentaerythritol.

We have now found that, surprisingly, an improvement in the stabilizing action is achieved, without discoloration of the polyamide matrix, particularly in the presence of pigments, if the stabilizers used are compounds of the general formula In these formulae, the symbols X, R and Y have the following meanings: 'X is NH or R is a carbonylalkyl or carbonylaryl group in which the alkyl radicals are branched-chain or, preferably, straight chain hydrocarbon radicals of from 1 to carbon atoms, and the aryl radicals are phenyl or naphthyl radicals which may be substituted at any position, and

Y is where R is a radical derived from aliphatic, aromatic or aromatic/aliphatic diisocyanates and R is a radical derived from aliphatic or aromatic dicarboxylic acids. Depending on the meanings of the radicals X and Y, the compounds to be used in the present invention may be divided into the following groups:

id mides i2 (NW3); H

I no cn -cn -c-NH-R III CH3 C(CH3)3 esters 1 no cH -cH -c-o-R IV C(CH3)5 bis-ureas b1sac1d amides) C CH C CH HOGCH -CH -(J-NH-C-H -C-NH-C-CH -CH OH VI I CH CH CH9; 3 3 Non Specific examples of the various compounds suitable for stabilizing polyamides according to the present invention are:

acid amides III may The compounds to be used in the invention are derived from 2,6-di-t-butylphenyl-butylamine and 2,6-dit-butylphenol-butanol.

The compounds to be used in the present invention may be prepared by methods known in the art to which no claim is made herein, for example according to the following scheme:

2 Raney- N1 2, 6-d1-t-butylphenol-butylamine Li ll 01- -R-C-C1 OCN-R-NCO acid amides III bis(acid amides) VI bis-areas V CH CH gH-CH compounds such as lactams, diamines and dicarboxylic acids and aminocarboxylic acids. Examples of polyamide-forming lactams are pyrrolidone, eaprolactam, capryllactam, enantholactam, aminoundecanolactam and lauroyllactam, which may be polymerized by cationic mechanisms either alone or in admixture with each other. Polycondensates ofdiamines and dicarbox- 2, G-di-t-butylphenol-butanol R-COOH esters IV The amount of stabilizer used is usually from 0.01 to 55 ylic acids are for example those producible from ali- 2% and preferably from 0.l to 1%, by weight of solid polymer. The stabilizer may be added to the polyamide-forming monomers prior to polymerization or to the mixture during polymerization, or they may be incorporated into the finished polyamide after polymerization. Suitable processes are those usually employed for this purpose, as described for example in Kunststoff-Handbuch, Vol. VI, Polyamide, Edited by R. Vieweg and A. Muller, published by Karl Hanser Verlag, Munich, 1966. The stabilizing action extends over all polyamides and copolyamides and polyamide mixtures produced from the well-known polyamide-forming phatic discarboxylic acids of from 4 to l8 carbon atoms and diamines of from 4 to 18 carbon atoms, particularly nylon 6.6 and nylon 6.10. There are obtained polyamides which are free from discoloration and which show greatly improved stability of their properties over the use of conventional phenolic stabilizers even when subjected to high thermal stresses and strong oxidizing attacks. The stabilizing action applies both to polyamides intended for the manufacture of shaped articles and to those intended for the preparation of fibers and filaments. The stabilizers of the invention are particularly suitable for use in colored polyamides, since the color values are not impaired thereby. This is particularly applicable to polyamides containing pigments. It is of no detriment when the polyamides also contain conventional fillers, glass fibers, other polymers, lubricants, crystallia ation accelerators and other conventional additives and other stabilizers.

The following Examples illustrate the above method of polyamide stabilization and the activity of the stabi lizers used. The parts are by weight. The percentages are by weight. based on the polymer product stabilized. The characteristic mechanical property taken as a measure of the aging properties (thermal resistance) was the perforated notched impact resistance. which was measured on standard specimens according to German Standard DIN 53,453. A hole having a diameter of 3 mm was drilled in the center of the said specimens measuring 4 X (i X 50 mm and the specimens were stored in air for 30 days at I40C. Tests were carried out after 3. I0, 20 and 30 days, each test consisting of the determi- EXAMPLE 2 Example I is repeated using 200 parts of polycaprolactam granules having a K value of 72 and l part each of the stabilizer compound and pigment listed in Table 2 below. The results are listed in Table 2.

EXAMPLE 3 nation of the perforated notched impact resistance on Example 2 is repeated using 200 parts of polyhexaten specimens, as described in "Kunststolie 57 methylene adipamide granules having a K value of 72 I967), pp. 825 to 828. (1% w/w in cone. H 80 in place of polycaprolactant ranules. The results are listed in Table 3 below. EXAMPLE I g 200 parts of polycaprolactam granules having a K value of 72 (l% in cone. sulfuric acid) are mechani- TABLE I Stabilizer Color Impact resistance (notched. perforated) (cmkg/cm) after t) 3 ll] Zll 30 days none colorless (it) I!) 1.0 ",9 1114 1 4 as starting HO -CH,CH, HNH(I.|ICH,IH-CH,| polyamide 6L5 43.7 30R R 5 LR fiNH-1H ('H. .-(H, 0H 73.7 74.0 30.41 2.7 l R Ho CH,-(H,-1H0-H(CH,) -CH;, out 40.x 2m so I 5 H0 -(.H, CH,-CH -NHl---NH (CH,],,-- 05.0 55.0 45.9 14.3 3.0

OH an} 40.! Zuu 8.5 1.8

TABLE l-continued Stabilizer Color Impact resistance (notched, perforated) (cmkg/cm") after 3 [0 20 30 days NHCNH-iHCH,-CH,- OH

as starting 86.6 69.0 47.l [3.8 3.0 polyamide NHCO-NHEHCH,CH, OH

1 E H0 CH,CH,$HNHC(CH,),,- NHCHCH;,

CH H, 61.6 56.0 43.8 l2.0 2.0

TABLE 2 Stabilization of pigmented nylon 6 (Example 2) Stabilizer Pigment Color Impact resistance (notched. erforatedXcmRg/cm') after 0 3 I0 20 30 days i HO CH,CH, HNHANH (CH Cadmium lemon 7L2 64.2 58.8 l6.0 2.6

yellow 6 ON yellow ":1 a

" Cadmium cherry red 68.0 53.5 458 10.3 L8

red BBS Cu corn lex of ethanolamine diacetic acid Br Cadmium dirty yellow 6 ON yellow 46.6 1.8 L1 0.9 0.8 Cadmium red dark red 20.2 3.4 L] 0.9 0.9

BBS

TABLE 3 Stabilization of nylon 6.6 (Example 3) Stabilizer Pigment Color lm act resistance (notched. per oratedXcmkg/em') after 3 10 day:

none none pale 68.0 2 .2 1.0 0.8 0.8

HO CH,-CH, H-NH-C-NH (CH,),- none an ltarting polyamide 67 SS l0.3 4.5 H11 3 TABLE 3-continued Stabilization of nylon 6.6 (Example 3) Stabilizer Pigment Color Impact resistance (notched. pcrforatedXcmkg/cm') after 3 I0 20 30 days Cu comlrlex of clhanolarnine diacetic Sachtolith pale 67.0 52.3 38.5 9.8 2.0 acid Br HD none slightly darker than 62 50 48 30 starting polyamide Sachtolith pale gray 26.2 L7 0.9 0.8 0.8

We claim: H i I )3 CH l. A process for stabilizing polyamides against oxida- H 3 tion and thermal degradation, which com rises incor- H0 CH -CH -CH-NH-C- p 2 2 n 2 i l 3 porating therein 0.0] to 2% by weight, based on said x=f o polyamide, of a stabilizing compound of the formula C )3 X a); Ex I C CH); 9) 8 0H CH -CH -EJ-X-R H0 CH CH -CH-NH-C- or CH C(CH 3 C(cH JB on o Z B tl in which X denotes NH--, and R denotes a carbony- HQ CH -CH -EJH- NH-C 0H lalkyl or carbonylaryl group in which the alkyl moieties are branched-chain or straight-chain hydrocarbon radi- C CH C 5) 3 cals of from I to 20 carbon atoms, and the aryl moieties 3 3 are phenyl or naphthyl radicals which may be substituted at any position.

2. A process as claimed in claim 1 wherein said stabilizing compound is cum 9 3 y no CH2-CH2-CH-NH-CCH3 3. A process as claimed in claim I wherein said amount of said stabilizing compound is in the range of 0.] to 1%.

4. A process as claimed in claim 1 wherein said polyamides are polylactams of pyrrolidone, caprolactam, capryllactam, enantholactam, aminoundecanolactam, lauroyllactam or mixtures thereof.

5. A process as claimed in claim I wherein said polyamidcs are polyamide polycondensates of aliphatic dicarboxylic acids of from 4 to l8 carbon atoms and aliphatic diamines of from 4 to 18 carbon atoms.

6. A process as claimed in claim 1 wherein said polyamides are nylon 6,6 or nylon 6,10 polyamides.

'l l l l t 

1. A PROCESS FOR STABILIZING POLYAMIDES AGAINST OXIDATION AND THERMMAL DIGRADATION, WHICH COMPRISES INCORPORATING THEREIN 0.01 TO 2% BY WEIGHT, BASED ON SAID POLYAMIDE, OF A STABILIZING COMPOUND OF THE FORMULA
 2. A process as claimed in claim 1 wherein said stabilizing compound is
 3. A process as claimed in claim 1 wherein said amount of said stabilizing compound is in the range of 0.1 to 1%.
 4. A process as claimed in claim 1 wherein said polyamides are polylactams of pyrrolidone, caprolactam, capryllactam, enantholactam, aminoundecanolactam, lauroyllactam or mixtures thereof.
 5. A process as claimed in claim 1 wherein said polyamides are polyamide polycondensates of aliphatic dicarboxylic acids of from 4 to 18 carbon atoms and aliphatic diamines of from 4 to 18 carbon atoms.
 6. A process as claimed in claim 1 wherein said polyamides are nylon 6,6 or nylon 6,10 polyamides. 